1. Field of the Invention
The present invention relates generally to integrated circuits, and more particularly to managing power on integrated circuits using power islands.
2. Description of the Prior Art
One design goal for integrated circuits is to reduce power consumption. Devices with batteries such as cell phones and laptops especially need a reduction in power consumption in the integrated circuit to extend the charge of the battery. Additionally, a reduction in power consumption prevents overheating and lowers the heat dissipation of the integrated circuit, which in some cases, eliminates or simplifies the heat sinks and/or fans for the integrated circuit.
Some integrated circuits are designed using building blocks of library cells. These library cells are blocks of circuitry performing a function. Some examples of library cells are NAND gates, multiplexers, decoders, comparators, and memory.
In a “full-custom” flow, the integrated circuit is designed at the lowest level such as at the individual transistors, capacitors, and resistors level. The “full-custom” flow may use library cells that are internally developed. The integrated circuit can have optimal performance because the integrated circuit is designed in great detail at the lowest level. However, some problems with the “full-custom” flow are the long time and expensive costs associated with designing at such a detailed level. Furthermore, the “full-custom” flow is cumbersome because the design is at the lowest level.
In a “standard-cell” flow, the integrated circuit is designed using library cells acquired from a third party or other outside source. These library cells are standardized at the logic or function level. The design time for the standard-cell flow is reduced because the library cells are already pre-designed and pre-tested.
In one example for designing an integrated circuit, the library cells are selected, and the custom logic is specified to build the integrated circuit. The register transfer level (RTL) for the integrated circuit is then written for simulation and debugging. After simulation and debugging, the synthesis is run for the integrated circuit. Performance measurement software is executed to determine performance of the integrated circuit. The final synthesis of the integrated circuit can then be run based on the optimal performance of the integrated circuit.
One problem with many integrated circuits is that power consumption is not efficiently utilized. For example, the entire integrated circuit may operate at a maximum frequency just to support an application needing that maximum frequency, while other portions of the integrated circuit can operate at a lower frequency. In another example, inactive circuitry within the integrated circuit consumes power and increases the likelihood of leakage. Inefficient power consumption may also adversely affect performance of the integrated circuit.
With the growing complexity of integrated circuits, the reduction of power consumption is even more important when the integrated circuit employs more functionality. One example of an integrated circuit is a system-on-a-chip that includes a microprocessor, memory, I/O interfaces, and an analog-to-digital converter all in a single chip. With many different types of functionality employed within a single chip, the system-on-a-chip consumes even more power than single function integrated circuits.
Some prior integrated circuits have employed voltage islands or multiple clocks to lower power consumption. One problem with these integrated circuits is that the voltages in the power island and the frequencies of the multiple clocks are static. The voltages and the frequencies do not dynamically change based on the needs and operation of the integrated circuit.